The invention relates to insulated fluid storage units, including hot water heaters.
Hot water heaters for domestic and other applications include an inner storage tank having an associated heating unit for heating water in the tank. The tank is enclosed with suitable insulation to retain the heat and minimize the necessity for frequent reheating. An outer aesthetically pleasing jacket or shell is provided to enclose the insulation.
A highly satisfactory insulating material is expandable foamed insulation such as expanding foamed polyurethane. The insulation is applied in a fluid state into the annular cavity space between the inner storage tank and the outer jacket and foams and expands to produce a rigid and closely adhering insulating enclosure about the inner tank.
Gas water heaters are provided with a burner aligned with the bottom of the storage tank. A skirt ring supports and spaces the tank above a support surface or base and defines a firing chamber. Polyurethane produces toxic fumes when burned, and hence must be protected from the temperature and flame of the heating unit. Various isolation sealing dams have been devised to deal with this problem, such as an inflatable donut bag, Clark et al U.S. Pat. No. 4,372,028, Tilton U.S. Pat. No. 4,477,399, a fiberglass collar, Pfeffer U.S. Pat. No. 4,749,532, Nelson U.S. Pat. No. 4,736,509, and an envelope bag, Denton U.S. Pat. Nos. 4,447,377, 4,527,543.
The present invention provides an improved dam which is simple and cost effective in manufacture.